There's nothing as relaxing as lying in a hammock, eyes closed, listening to the birds sing. It's even better if you can identify the feathered friends you're hearing. Thanks to the Internet, recordings of bird calls are only a click away. Take a listen, and soon you'll recognize which birds are serenading you ... without even having to open your eyes. Learn more about bird calls:

Cornell Lab of Ornithology: Learn about more than 500 species of birds, browse photographs, and see maps of where the birds can be found.